Prostate cancer is the second largest cause of cancer mortality among males in the United States (U.S.). Despite the importance of this cancer, little is known about its etiology. The proposed study investigates the hypothesis that Vitamin D deficiency may be a risk factor for prostate carcinoma. This hypothesis is based on the observation that the geographic distribution of prostate cancer parallels closely the availability of ultraviolet radiation, the principle determinant of Vitamin D levels. The higher prostate cancer rates observed among Blacks versus Whites in the U.S., and between U.S. Blacks versus African Blacks, are also interpretable on the basis of Vitamin D deficiency. The hypothesis is consistent with recent experimental data which indicate that Vitamin D inhibits the expression of cellular oncogenes that are amplified in human prostate cancer cells. The hypothesis will be tested in a case-control study of 50 patients with prostate carcinoma and 50 patients with benign prostatic hypertrophy as controls. Cases and controls will be compared with respect to their serum concentrations of Vitamin D metabolites and the allelic distribution of D-Binding Protein. Differences in skin pigmentation and solar exposure habits will also be measured and compared.